There are several language families in Mexico which are not presently believed (by most linguists) to be related to other families.
In some cases, proposals have been made to link them to others, but the evidence is not generally considered convincing. We refer to these languages as language isolates.
These language families, whether large and geographically extensive (like Mayan) or small (like Serian), may be the only surviving members of much larger language groups which were mostly absorbed by other language groups in centuries or millennia past.
Huave (also spelled Wabe) is a language isolate spoken by the indigenous Huave people on the Pacific coast of the Mexican state of Oaxaca. The language is spoken in four villages on the Isthmus of Tehuantepec, in the southeast of the state, by around 18,000 people.
Purépecha was the main language of the pre-Columbian Tarascan state and became widespread in north western Mexico during its heyday in the late post-classic period (~ 1400-1521). It is a language isolate or small language family spoken by more than 100,000 P’urhépecha people in the highlands of the Mexican state of Michoacán. Even though it is spoken within the boundaries of Mesoamerica, Purépecha does not share many of the traits defining the Mesoamerican Linguistic Area, probably due to a long adherence to an isolationist policy.
The term Serian family may be used to refer to a language family with Seri as its only living member; related languages have disappeared in the last couple of centuries.
Attempts have been made to link it to the Yuman family, to the now-extinct Salinan language of California, and to the much larger hypothetical Hokan family. These hypotheses came out of a period when attempts were being made to group all of the languages of the Americas into families. In the case of Seri, however, very little evidence has ever been produced. Until such evidence is presented and evaluated, the language is most appropriately considered an isolate.